www.bonaireturtles.org Dutch Caribbean Nature Alliance Safeguarding nature in the Dutch Caribbean earth outreach DCNA © 2012; The Great Migration Game; Conservation Handbook No. 008; Dutch Caribbean Nature Alliance, Dutch Caribbean. Dutch Caribbean Nature Alliance Safeguarding nature in the Dutch Caribbean Prepared by Cathrin Jerie and DCNA Dutch translation by Maarten Schuit Graphic design by Robert Jan van Oosten All photos from Sea Turtle Conservation Bonaire unless specified within DCNA’s activities are funded through the support of the Dutch Postcode Lottery and the Dutch Ministry of Interior (BZK) great migration game 2 great migration game great migration game Bonaire’s sea turtles Seven species of sea turtles inhabit the world, and three of those species are found on Bonaire. All of the species are endangered and facing extinction. Many sea turtles are being captured, on purpose or accidently, and their nesting beaches and coral reef feeding areas are being degraded and destroyed. Bonaire is one of a few safe havens for sea turtles. From April to December each year, adult green turtles (turtuga blanku), hawksbill turtles (turtuga karet), and loggerhead turtles (turtuga kawama) migrate to Bonaire to breed and nest. Young green and hawksbill sea turtles, however, can be found throughout the year feeding around the island, having drifted from their birthplace to forage around Bonaire. These young sea turtles grow and build their strength before leaving Bonaire to return to their birthplace to breed and nest. Green turtles and all sea turtles enjoy a protected status on Bonaire. The young sea turtles find plenty of their favorite food on the island, particularly at Lac Bay. Our re- search has shown that these green turtles grow faster on Bonaire than anywhere else in the world. Green turtle - Robert van Dam 4 great migration game Turtle hatchling Hawksbill turtles are critically endangered worldwide. Many people harvest their eggs and use their shells, threatening the species with extinction. While hawksbill turtles nest throughout the Caribbean, they do not nest in large concentrations and every beach where they nest is critical to the species’ survival. Endangered loggerhead turtles come to Bonaire only seasonally as adults to breed and nest. Females lay their eggs on the southwestern beaches and on Klein Bonaire. Nesting female sea turtles will lay an average of three to six clutches of eggs, deposit- ing 100 to 180 eggs per nest, depending on the species. Once a nest is laid, the female returns to the sea, leaving the eggs to incubate in the warmth of the sand. Eggs hatch after about two months. The entire nest hatches at the same time, and the hatchlings (baby sea turtles) scramble together to the sea. fun fact Turtles evolved hundreds of millions of years greatago. These migration ancient reptiles havegame 5 lived on earth since the time of the dinosaurs. The green turtle (Chelonia mydas) The green turtle has a round face and its carapace scutes (shell plates) do not overlap. Green turtles weigh as much as 230 kg (about 500 lbs.), although most on Bonaire are much smaller because they usually are not yet fully grown. While they sometimes eat jellyfish, they mainly are vegetarians (herbivores) and eat seagrasses and algae. Adult green turtles usually are found on Bonaire only during the nesting season, while younger turtles live on the island year-round. Green turtle eating seagrass - Robert van Dam The hawksbill turtle (Eretmochelys imbricata) The hawksbill turtle has a pointed face with a mouth like a hawk’s beak. Its shell plates overlap, and the edge of its carapace is serrated toward the rear of its body. Hawks- bills weigh as much as 85 kg (about 185 lbs.), and their diet mainly consists of coral reef sponges. Bonaire hosts young hawksbills year-round. Most adults are present only during the nesting season. The loggerhead turtle (Carreta carreta) Hawksbill over reef - Doug Cohen The loggerhead has a massive head that is broad and triangular. Its shell is often encrusted with barnacles, and its front flippers are relatively short compared with other species. Loggerheads can weigh as much as 200 kg (about 440 lbs.). Loggerheads are carnivores (meat-eat- ers) and use their powerful jaws to crush and eat crabs, clams, snails, jellyfish and other invertebrates. Sightings of loggerheads on Bonaire almost always are of adults that have come to breed and nest. Loggerhead adult - Irene da Cunda Knowing that many Bonairean sea turtles forage in our waters, we can coordinate and strengthen conservation efforts to reduce the many dangers for sea turtles locally. In addition to natural predators, the sea turtles are endangered by ocean trash and pollu- tion. They can become entangled in cast off fishing line or in some fishing nets and drown. Coastal development, pollution and climate change all are affecting sea turtle populations. 6 great migration game QUIZ How many species of sea turtles can be found on Bonaire? How many clutches of eggs do female sea turtles typically lay? Which species come to Bonaire only as adults? Which species is critically endangered? What is the scientific name for the sea turtle’s shell? What is the scientific name for a sea turtle’s shell plates? What term refers to baby sea turtles? Match the Latin name to the correct English name: Carreta carreta Green turtle Chelonia mydas Hawksbill turtle Eretmochelys imbricata Loggerhead turtle What factors are affecting sea turtle populations? fun fact great migration game 7 Female turtles typically lay up to six ‘clutches’ of more than 100 eggs. Migration Sea turtles are migratory. Throughout their lives, adult sea turtles migrate between their nesting sites and their foraging grounds. Bonaire’s female breeding sea turtles return to the island for two to four months every two to three years to nest. Males, however, return every year to breed. The sea turtles then leave Bonaire waters to journey hundreds or thousands of kilometers to their foraging grounds. Green turtle - Robert van Dam STCB’s Satellite Tracking Program has shown that the sea turtles swim distances from 250 km to 2,500 km over two to six weeks to return to the ocean around Nicaragua, Honduras, Mexico and Colombia to the west; Puerto Rico, Jamaica, the Dominican Republic and the Virgin Islands to the north; and Venezuelan coastal areas and islands to the south and east. How sea turtles navigate so well to specific geographic targets is still pretty much a mystery to humans. To make such a migra- tory journey, the sea turtle needs to maintain its headings — compass sense — and also a sense of where it is in relationship to its goal — or map sense. Many animals have a sense of compass based on stars, the sun’s position, patterns of skylight polariza- tion, and the Earth’s magnetic field. We have much to learn about the mechanisms Transmitter up close that underlie sea turtles’ and other migratory animals’ map sense. Recent experiments indicate that the sea turtles’ map sense is based at least partly on the Earth’s magnetic field. 8 great migration game Protected areas for Hawksbill sea turtles QUIZ How often do female sea turtles return to Bonaire to breed and nest? How often do males return? How far might sea turtles migrate between their nesting and foraging areas? On the map, find and circle places where Bonairean sea turtles forage. What does the latest research indicate about how sea turtles navigate? fun fact The temperature of the sand around a nest determines whether baby turtles, 9 known as ‘hatchlings’, will be male or female. greatColder temperatures migration produce game males and warmer temperatures produce females. tracked sea turtles map Cuba Jamaica Honduras Nicaragua Costa Rica 10 great migration game Haiti Dominican Republic Jklynn Caribbean Sea Aruba Curaçao Bonaire Venezuela fun fact Turtles drink saltwater and get rid of extra salt greatthrough special migration glands game 11 in their eyes. Previously tracked sea turtles Turtles are in some ways like people. They are individuals. Every turtle has a differ- ent shape and a different pattern on its carapace, head and even flippers. Every turtle also has its own story. Tracking captures a piece of the individual turtle’s story of its journey to Bonaire and back to the reef it calls home. Staff and volunteers have been hard at work to tag turtles and track their migration journeys. Hawksbill turtles Nautila Nautila, a female hawksbill, was the first-ever tracked sea turtle from Bonaire. She was fitted with a transmitter on Oct. 24, 2003, and left Bonaire’s waters the very next day. She traveled 1,712 km in 45 days before arriving at Navidad Bank, 100 km north of the Dominican Republic. To this date, no other tracked sea turtle has ever traveled that far north. Schillie Schillie is a female hawksbill tagged in 2003. On her journey, she first reached the Dominican Republic and then made a little de- tour. She swam 200 km back toward Bonaire before changing her mind and turning around again. In January 2004, she reached her home base near Monito Island, Puerto Rico. In August 2005, a Sea Turtle Conservation Bonaire researcher doing an in-water survey in Puerto Rico spotted her and removed her transmitter. Tom Tom is the first male hawksbill turtle tracked on Bonaire. After he was fitted with a transmitter in July 2004, he remained around the island for almost 100 days to mate. Next, he headed toward the Saba Bank, and his signal was lost. When he returned the following year to mate in Bonaire, Sea Turtle Conservation Bo- naire staff saw him and removed the transmitter. As a male sea turtle, he usually returns every year to his breeding ground.